MANKATO - Vikings coach Leslie Frazier announced star running back Adrian Peterson's return to active duty with a smile and strong words of caution that couldn't have been more clear had they come with yellow flags and a giant banner screaming "Mission NOT Accomplished!"

"I want to caution you," Frazier said after Peterson was taken off the physically-unable-to-perform (PUP) list on Sunday morning. "I know there are a lot of fans that are very optimistic and excited about seeing him back. But for us, it's just a part of the process. It doesn't mean a whole lot other than he's done a great job in his rehab up to this point.

"He's done everything he can do on the side, and now it's the next step in the process. It doesn't mean in the future he's going to be lining up with our team in the opening game [against Jacksonville on Sept. 9]. We don't know that."

Now, whether fans and media choose to listen is, well, another matter. After all, the sight of the Vikings' four-time All-Pro taking a handoff from Christian Ponder during Sunday morning's walk-through was the most vivid indication that Peterson just might succeed in his quest to redefine the timetable for NFL players returning from the kind of devastating knee injury he suffered at Washington on Christmas eve.

See. There we go. Looking too far ahead while wondering how a man made of flesh and bone -- and a lot of muscle -- has come this far in 7 1/2 months since his Dec. 30 surgery to repair torn anterior cruciate and medial collateral ligaments in his left knee.

"I was like a kid in a candy store today when I came out here and they threw me in with the first group," Peterson said. "I was smiling. I had to try to calm myself down. I was going a little too fast for a walk-through in the beginning. For me, this is so satisfying. I had a lot of people doubting me and saying this and saying that. But I kept my faith and kept working hard. Now, I'm back in the mix."

Per rules of the collective bargaining agreement, Peterson can't put full pads on until he's been through two practices. So he'll be limited to walk-throughs and individual drills until putting the pads on Tuesday. He also won't be tackled to the ground when the Vikings run their short-yardage and goal-line drills.

Peterson almost certainly won't play in Friday's second preseason game against the Buffalo Bills at Mall of America Field. A more likely target is the third preseason game against the San Diego Chargers a week from Friday at Mall of America Field. The fourth preseason game at Houston is unlikely; teams typically rest most, if not all, of their starters in that game.

Peterson initially was told that his rehab would take nine months. But Frazier doesn't seem surprised that Peterson will be in pads before the second week of the preseason.

"Maybe if it were somebody else," Frazier said. "But with Adrian, he's unique and he's always been that way in the time I've known him in his career. He's special in so many ways."

But, again, Frazier tried to temper the perception that Peterson is all the way back. Going from pads to being game-ready and taking a hit is "a huge step," Frazier said.

"When you are in situations that aren't choreographed, to have to react will be a big step when that time comes," Frazier said. "Where guys can hit you anywhere, they can hit you low, they can hit you high. That's a big hurdle. Not just from a physical standpoint but from a mental one as well."

If you're one of those who may have doubted Peterson, he said you're not alone. He said he "sensed it" in some fans, media and, heck, even some of his family members.

"Some in the family weren't necessarily saying they're doubting [me], but they're not speaking the same words I'm speaking," Peterson said. "My vision, they're not seeing the same things. I know they love me and everything, but I'm in disagreement with them.

"It doesn't matter because I had my mind set on what I wanted to conquer. I knew it wasn't going to be easy. It was going to take work. I had my faith in the right place, my will in the right place. I'm back."

Chris Colabello hit a two-run home run, R.A. Dickey threw seven shutout innings and the Toronto Blue Jays beat the Kansas City Royals 5-2 in testy matchup Sunday, taking three of four from the AL's top team.

Charlie Morton pitched five-hit ball for seven innings, Neil Walker hit a review-aided home run and the Pittsburgh Pirates beat the Cincinnati Reds 3-0 Sunday in a testy game in which benches cleared after stars Andrew Mcutchen and Brandon Phillips were hit by pitches.